This invention relates to fiber gratings, and more particularly to a compression-tuned Bragg grating and laser.
It is known in the art of fiber optics that Bragg gratings embedded in the fiber may be used in compression to act as a tunable filter or tunable fiber laser, as is described in U.S. Pat. No. 5,469,520, entitled xe2x80x9cCompression Tuned Fiber Gratingxe2x80x9d to Morey, et al and U.S. Pat. No. 5,691,999, entitled xe2x80x9cCompression Tuned Fiber Laserxe2x80x9d to Ball et al., respectively, which are hereby incorporated herein by reference.
To avoid fiber buckling under compression, the technique described in the aforementioned U.S. Pat. Nos. 5,469,520 and 5,691,999 uses sliding ferrules around the fiber and grating and places the ferrules in a mechanical structure to guide, align and confine the ferrules and the fiber. However, it would be desirable to obtain a configuration that allows a fiber grating to be compressed without buckling and without sliding ferrules and without requiring such a mechanical structure.
Also, it is known to attach an optical fiber grating to within a glass tube to avoid buckling under compression for providing a wavelength-stable temperature compensated fiber Bragg grating as is described in U.S. Pat. No. 5,042,898, entitled xe2x80x9cIncorporated Bragg Filter Temperature Compensated Optical Waveguide Devicexe2x80x9d, to Morey et al. However, such a technique exhibits creep between the fiber and the tube over time, or at high temperatures, or over large compression ranges.
Objects of the present invention include provision of a grating configuration that allows the grating to be compression-tuned without creep and without requiring sliding ferrules or a mechanical supporting structure for the ferrules.
In accordance with an embodiment of the present invention, a tunable optical filter comprises a compression-tuned optical device comprises an optical waveguide including an inner core disposed within an outer cladding. The optical waveguide further includes a grating disposed within the inner core. The grating reflects a first reflection wavelength of light back along the inner core and propagates the remaining wavelengths of light through the grating. The optical waveguide includes a pair of opposing surfaces. A compressing device engages the opposing surfaces of the optical waveguide for compressing the opposing surfaces towards each other. The compression of the opposing surfaces tune the grating to change the reflection wavelength of light reflected back along the inner core.
In accordance with another embodiment of the present invention, a method for wavelength-tuning an optical device comprises providing an optical waveguide including an inner core disposed within an outer cladding. The optical fiber further includes a grating disposed within the inner core. The grating reflects a first reflection wavelength of light back along the inner core and propagates the remaining wavelengths of light through the grating. The optical waveguide includes a pair of opposing surfaces. The method further comprises compressing the opposing surfaces of the optical waveguide towards each other to tune the grating to change the reflection wavelength of light reflected back along the inner core.
The foregoing and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of exemplary embodiments thereof.